This application claims the priority of German Patent Application Serial No. 199 58 431.1, filed on Dec. 3, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to a cable assembly and a method of making the same.
For the production of cable assemblies or cable harnesses, a plurality of elongated cable elements, such as electrical and optical strands, are normally laid out along a desired path and plastic material is then foamed, poured or sprayed around them. Following the cooling and hardening of the plastic material, the cable elements are combined as bundles following a predetermined path inside a hardened plastic sleeve body and are secured in this way. During the manufacture of the sleeve body or the outer sleeve shell the thermally sensitive cable elements, such as optical wave guides, can be damaged by the hot plastic material and excessively high temperatures. Furthermore, the bundling and/or predetermined specific layout of the respective cable element involves the danger that mechanically sensitive cable elements are subjected to an excessively high lateral pressure or are excessively bent or kinked, thus subjecting them to an impermissibly high mechanical stress.
A design using a molded plug to render a cable assembly longitudinally watertight is disclosed in German Offenlegungsschrift (application published without examination) No. 37 42 731, while a method of guiding conductors through a cable assembly within a protective tube is known from published British Application No. 21 81 605.
It is an object of the invention to provide an improved arrangement for producing cable assemblies easily and in a more reliable manner.
This object is achieved according to the invention with a cable assembly of the aforementioned type in that the cable assembly comprises at least one protective tube which accommodates at least one cable element to protect it against thermal and/or mechanical stresses. The protective tube is furthermore provided with at least one transverse port on the inside tube wall. Plastic material used for the sleeve body flows during manufacture through the transverse port from the outside to the inside, such that the protective tube is filled watertight in the longitudinal direction in the region where the material flows in.
By providing at least one protective tube inside the plastic material of the sleeve body for the mechanically and/or thermally sensitive cable elements, such as optical wave guides, it is ensured that such sensitive cable elements are protected against excess thermal and/or mechanical stresses. The protective tube therefore provides a thermal barrier or screen for the cable elements it surrounds during the production of the sleeve body by virtue of pouring on or foaming on the plastic material. Thus, the cable element inside the protective tube is not directly subjected to the hot plastic material used for producing the sleeve body. The protective tube at the same time represents a mechanically reinforced passage inside the plastic material of the sleeve body, which provides additional mechanical protection for the cable assembly against bending stresses. Furthermore, if two groups of different thermally and/or mechanically sensitive cable elements are to be combined by a cable assembly, the protective tube makes it possible to accommodate the more sensitive cable elements inside the protective tube and thus separate them from the thermally and/or mechanically less sensitive cable elements. In addition, the protective tube ensures to a high degree that lateral pressure forces, that may be due to the bundling of several cable elements or the clamping of the beginning and the end of the bundle to direct the cable elements onto a desired path, can substantially be kept away from the cable elements inside the protective tube.
Liquid plastic material can penetrate into the protective tube during the production of the sleeve body since at least one transverse port is provided in the wall of at least one longitudinal section of the protective tube. The protective tube is therefore cross-sectionally filled so as to be substantially watertight in the longitudinal direction in the region of the transverse port. The protective tube is thus longitudinally sealed at the same time as the sleeve body is produced and as part of the same step. Thus, no additional operation is needed for providing a longitudinal watertight seal for the protective tube.
A further feature of the invention provides that the transverse port inside the protective tube is advantageously dimensioned such that the protective tube is filled with the inflowing plastic material so as to render it watertight, but only over a partial tube length. Thus, first, there is effected a targeted metering of the plastic material into the protective tube, so that the amount of the inflowing plastic material is sufficient to ensure a tight longitudinal sealing of the protective tube. Second, the flow of hot plastic material is simultaneously regulated to allow only enough plastic material to enter the protective tube to ensure that an excess thermal stressing of the sensitive cable elements inserted therein is substantially avoided. The protective tube therefore is not filled along the entire tube length with the plastic material, but only locally, along a partial section of its total length.